Mix together the ground chuck, egg, milk, and onion soup mix. Spread on a 9x13 cookie sheet, very thinly. Sprinkle with chopped onion.
Bake in preheated oven at 350°F for 10 to 15 minutes.
While baking, split two packs of Pepperidge Party Rolls in half horizontally, leaving bottoms attached to each other. Put a dill pickle slice on each bun. Cut meat in half. Salt and pepper to taste. Place on the buns. Top with bun. Slice to serve.